The present invention relates to a nondestructive diagnostic method and apparatus which can nondestructively and optically diagnose the weight reduction ratio of an insulating material, a structural material, a lubricating oil or the like, which is used in equipment, irrespective of whether it is a liquid or solid, without stopping the operation of the equipment.
As a nondestructive diagnostic apparatus for evaluating the degree of deterioration of an insulating material in a rotating machine, Japanese Patent Laid-Open Publication No. Sho 64-84162 discloses a diagnostic apparatus in which an irradiated light beam supplied from a white standard light source and directed by an optical fiber is reflected by a sensor unit made of a material which is the same as the insulating material. The reflected light beam is detected via a light receiving optical fiber, and a color specification arithmetic operation is executed by using chromaticity or a difference in chromaticity, based on the L*a*b* color specification system. L* is a lightness index showing lightness and a* and b* are called chromatic indices showing chromaticity (hue and saturation).
According to the conventional technique mentioned above, when equipment, such as a rotating machine, is produced, it is necessary to preliminarily embed the irradiation optical fiber, the light receiving optical fiber, and the sensor unit in an insulating layer of the equipment. There is, consequently, a substantial problem in that the above technique cannot be applied to existing equipment in which those optical fibers and the sensor are not already embedded in the machine.
Further, the conventional technique cannot diagnose the weight reduction ratio of a material.